We Are All Africans

Nice hypothesis, you may say, but is it true? The heart of the scientific method lies in that skeptic's simple question. A merely plausible explanation of what we observe will not suffice, nor will a hypothesis bolstered only by some expert's endorsement. Modern science is wonderfully egalitarian, and it demands proof that all can see: measurements, objects or evidence of some kind. Scientific hypotheses must be both well-defined and firmly supported, preferably by several different types of data.

If a hypothesis meets these requirements, does this mean it is true? No, according to the philosopher Karl Popper, who believed that hypotheses could never be proven true—only false. Frederick Nietzsche claimed that the great charm of hypotheses was that they were refutable. While Nietzsche may be correct in the abstract, my experience suggests that scientists do not gleefully bury hypotheses in which they have invested many years of research.

In the study of human evolution, dueling hypotheses are commonplace because of long-standing, frequently erupting feuds about the interpretation of the fossil record. The field is so argumentative, in part, because the theories reflect directly on the nature and origin of humans. There is immense room for giving and taking offense when the subject is oneself. Too, the primary data of paleoanthropology—fossilized remains of our ancestors and near-relatives—are rare and difficult to obtain. Hence, it is not a simple matter to collect more evidence to clarify or support hypotheses. Fossil hunting requires tremendous knowledge and effort, good organizational skills, substantial grants, and a huge dollop of luck. New theories are, sadly, easier to come by than new primary evidence.

Thus it is a joyous occasion when my paleoanthropologist colleagues appear to resolve one of the most bitterly debated questions in the discipline: the issue of when, where and how modern humans evolved. For simplicity, I use "modern humans" or "recent humans" to denote the species to which I (and all the readers of this magazine) belong, but the formal term is either "anatomically modern Homo sapiens" or "Homo sapiens sapiens." Humans who lived in the past and did not have modern anatomy are often referred to as archaic or primitive.